What is Exobiology

1
What is Exobiology

• Exobiologists study how life may have originated
  here on Earth and where it may also exist in the
  universe.

2
What Is Life?

• 1. The basic units of life are cells.
• A. All living organisms are either single-celled
  or multicellular.
• B. Cells are bounded by membranes and contain
  DNA and RNA.
• 1. DNA contains the genetic code.
• 2. RNA translates the genetic code into proteins.

3
Other Properties of Life

• C. Living organisms reproduce either
  individually or in pairs.
• D. Living cells carry out complex chemical
  reactions to convert materials and energy for
  their own use (metabolism).

4
Two Types of Cells

• Prokaryotic cells contain no nucleus.
• 1. Bacteria are prokaryotic cells.
• 2. First organisms to show up in the fossil
  record are prokaryotes.
• Eukaryotic cells.
• 1. More complicated structure then prokaryotic
  cells.
• 2. Multicellular organisms have eukaryotic cells.

5
Two Types of Cells

6
Requirements For Life to Exist

• Significance of water.
• 1. Water is essential to the chemistry of all
  biological systems.
• 2. It is the medium in which biochemical
  reactions take place in.
• 3. In looking for signs of life either here on
  Earth or elsewhere scientists look for signs of
  liquid water.

7
Cells Are Made of Molecules

• All cells and their constituents are made of 4
  types of biomolecules.
• Carbohydrates sugars and starches.
• Proteins composed of amino acids.
• Lipids fats which are composed of long chain
  fatty acids, glycerol, phosphate groups, etc.
• Nucleic Acids DNA and RNA, composed of
  nucleotides. Adenine, Thymine, Guanine and
  Cytosine

8
Biomolecules are Organic Compounds

• Biomolecules are large molecules with a carbon
  skeleton.
• Organic compounds are those molecules that
  contain carbon.
• All life as we know it is based on carbon
  compounds.
• Did organic compounds arrive on earth via comets?

9
Origin of the Molecules of Life

• Miller-Urey Experiment.
• 1. Early atmosphere was believed to contain
  methane, ammonia, water and hydrogen.
• Miller created such an "atmosphere." It consisted
  of methane, ammonia, water and hydrogen above an
  "ocean" of water. Then he subjected the gases to
  "lightning" in the form of a continuous
  electrical discharge. After a few days, he
  analyzed the contents of the mock ocean.
• He found a mixture of organic compounds and amino
  acids in the artificial ocean.

10
Millers Experiment
11
Origin of Life on Earth (II)
Chemosynthesis 1st phase hydrocarbon chains
formation from ammonia, water and hydrogen (the
Miller - Urey experiment). These complex
molecules were formed in the air and accumulated
in the oceans.
12
Where Did Life Originate on Earth?

• Deep Sea Thermal Vents?
• A. First discovered in 1979.
• B. Scientists discovered whole ecosystems of
  organisms living in the absence of sunlight.
• Panspermia?
• A. Life arose from extra-terrestrial sources?
• Frozen Ocean Hypothesis?

13
Deep Sea Vent
14
Panspermia

• A theory developed by Svente Arrhenius.
• The theory states that life did not originate on
  the Earth, but originated elsewhere in the
  universe.
• Plausible if we find life on other worlds.

15
Frozen Ocean Hypothesis

• Three billion years ago, the Sun was thirty
  percent less luminous than it is today.
• The first 300 meters of the ocean was frozen.
• The layer of ice protected organic molecules from
  ultraviolet radiation.
• These organic molecules were supplied by
  hydrothermal vents.

16
(No Transcript)
17
The Search For Life Outside Earth

• The Planet Mars.
• 1. The Viking missions found no evidence of
  organic compounds in the Martian soil.
• 2. ALH84001.
• A. A meteorite found in Antarctica and
  determined to have originated from Mars.
• B. Along tiny cracks scientists discovered signs
  of what appears to be fossilized bacteria.

18
ALH84001

• There are four main clues which bring some
  scientists to this conclusion.
• 1. The meteorite is definitely of Martian origin.
• 2. The presence of complex organic molecules.
• 3. The presence of bacterial metabolites.
• 4. The pictures of the possible fossilized
  bacteria themselves.

19
ALH84001
20
Mars Pathfinder Mission

• This probe landed near the Ares Vallis region of
  Mars.
• This site may have been hot and wet at one time.
• This area may have been like the Yellowstone area
  where microbes flourish today.

21
The Little Rover That Could
22
Bacteria-the Space Colonists?

• I always thought the most significant thing we
  found on the whole _at_ Moon was that little
  bacteria who came back and lived and nobody ever
  said _at_ about it. Pete Conrad, Commander
  Apollo 12, 1969
• Mr. Conrad had a colorful way of expressing
  himself through the English language.

23
Bacteria-the Space Colonists

• On April 20, 1967, Surveyor 3 landed on the moon
  near Oceanus Procellarum.
• Aboard was a television camera.
• On November 20, 1969, Apollo 12 astronauts Pete
  Conrad and Alan L. Bean recovered the camera.
  When NASA scientists examined it back on Earth
  they found specimens of Streptococcus mitis that
  were alive.

24
Is There Life Elsewhere in The Solar System?

• NASA is currently looking at three other
  possibilities Mars, Europa and Titan.

25
Jupiters moon Europa

• Evidence from images taken by Galileo show
  regions resembling ice flows on Earth.
• The heat generated by tidal forces due to
  interactions with Jupiters gravity field may be
  enough to liquefy some portion of Europas icy
  crust.
• Could Europa support microbial life?

26
(No Transcript)
27
Saturns moon Titan

28
Saturns moon Titan

• Laboratory simulations show that a Titan-like
  atmosphere, primarily a N2/CH4 mixture, under
  various energetic excitations will form complex
  organic molecules and adenine, a component of DNA.

29
30 Million Year Old Germs

• In 1995, Biologists Raul Cano and Monica Borucki
  had extracted bacterial spores from bees
  preserved in amber in Costa Rica.
• When placed in a suitable culture, the spores
  came right back to life.
• The biologists also attempted to culture from the
  same amber a number of samples that contained no
  bee parts. These cultures were negative.

30
30 Million Year Old Bacteria
31
Conclusion

• Bacteria can resist adverse conditions by forming
  spores.
• Bacteria can live under an enormous wide range of
  conditions most of which would kill eukaryotic
  organisms.
• The main thing that bacteria need to survive is
  liquid water.
• If there is other life in our solar system it is
  most likely bacterial?